Theory Observation Distinction

Is there a genuine distinction between observable and unobservable entities? Why does it matter? How, and why, might one distinguish between theoretical and observational statements in science?

I have decided to tackle both these questions because they feed into and relate to one another. They emphasize different aspects of a prevalent debate, all aspects of which I wish to touch on. Whether the question of a distinction between observable vs unobservable entities is synonymous to the question of a distinction between theoretical vs non-theoretical statements is itself a matter of debate. Quine advocates semantic ascent, the shift in which the language we use to refer to the world becomes something we talk about in its own right. Semantic ascent is a shift from questions about objects to questions about words or statements. He says we should ‘drop the talk of observation and talk instead of observation sentences, the sentences that are said to report observations’ (The roots of Reference). So obviously Quine thinks the two questions are equivalent. They have often been treated as equivalent questions, or at least not distinguished too carefully. I agree with Van Fraassen that we should at least note and respect the differences between the two ways of talking about what might be the same issue, and not make the category mistake of talking about theoretical entities, just for clarities sake. At any event Paul M Churchland disagrees with Quine that the two debates are parallel , He says “we agree (Churchland and Van Fraassen) that the observable/unobservable distinction is entirely distinct from the nontheoretical/theoretical distinction”. This disagreement / confusion as to the very terrain, layout of the questions of the debate, arises because there is the ordinary language question of how do we naturally apply the terms ‘observed’ and ‘observation’, as well as the question of whether a principled O/T distinction can or should be drawn; as Gerry...